Thermostat



y 1942. c. s. MERTLER 2,239,061

THERMOSTAT Fiied Sept. 10, 1940 ff lNVENTOR Charles S. Merl-[en ATTORNEY Pa tented July 7, 1942 Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, .a corporation of Pennsylvania Application September. 10, 1940, Serial Np. 356,119

" 7 Claims.-

My invention relates to thermostats and more particularly to bimetallic snap-acting thermostats.

An object of my invention is to provide an I inexpensive, simple, highly sensitive, rugged bimetallic element for a snap-acting thermostat.

Another object of my invention isto provide an N-shaped bimetallic element for a thermostat which is adapted to be longitudinally constrained so as to provide a powerful snap-action thereof along a plane normal to the surface thereof.

A further object of my invention is to provide a thermostat having a longitudinally constrained bimetallic element which is adapted to move from one position to another with a snap action and which is associated with an adjustably posiis flexibly andjinsulatedly attached to the free end of the contact arm l8. The electrical path through the thermostat is say from terminal strap 22 through one stationary contact Hi, the cooperating movable contact 16, movable contact bar 26,, second movable contact l6, and the second stationary contact l4 to terminal strap 24.

tioned contact arm for energizing or deenergizing cooperating contacts.

Other objects of my invention will either be pointed out specifically in the course of the following description of a device embodying my invention, or will .be apparent from such description.

In the accompanying drawing:

Figs. 1, 2 and 3 are top, side and end views,

respectively, of the thermostatic structure embodying my invention; and

, Fig. 4 is a sectional view IV-IV of Fig. 2.

Referring to the accompanying drawing in taken along the line which-like reference characters indicate like parts in the several figures, I show a thermostat l0 comprising a supporting structure l2, cooperating contacts which include a pair of stationary contacts l4 and a pair of movable con- 1.

substantially N-shaped element 20 when in its free or unrestrained position (that is, before betacts IS, a movable or fulcrumly mounted contact arm [8 and a bimetallic element 20.

The supporting structure I2 is, in this instance, a flat stripof preferably insulating material. However: itis to be understood that any other suitable shape or configuration may be used in lieu thereof. A plurality of apertures are located within the structure l2 to support or retain suitable posts and operating members as hereinafter described. a w

I The cooperating contacts include a pair of stationary contacts l4 and a pair of movable contacts l6. vThe stationary contacts 14 may be insulated from and rigidly attached to the supporting structure l2, in any well known manner. In addition; the contacts l4 aresrigidly vattached to and electrically associated with-suitable metallic terminal straps 22 and 24. The movable contacts l6 are rigidly attached to a metallic flexible movable contact bar 26 whichnin turn,

The contact arm I8 is, in this instance an elongated relatively light sheet metal member which is adapted to be retained in position by means of a calibrating post 28 atone end thereof, and the adjusting screw 32 at the other end thereof. The contact end of arm l8 has a notch therein (not shown) which loosely fits about the calibrating post 28 permitting such arm to move with respect thereto. The other end of such arm I8 is, in this instance, substantially square and fits into slot 30 of adjusting screw 32. The lefthand or contact end of the contact arm I8 is thus adapted to freely move vertically along the calibrating post as a guide; and the entire arm is adapted to flex about the adjusting screw 32, as hereinafter described. v

The bimetallic element 28 comprises, in this instance, a substantially flat elongated bimetallic member having elongated slots 34 and 36 out from opposite ends of the element. In this way there is formed a substantially N or Z shaped member having-two exterior portions, strips,

or legs with free ends 42 and 44 connecting the respective exterior legs to a central leg. The

ing mounted on base I2) is considerably longer than when occupying the illustrated operative or constrained position. Note Fig. 1 which indicates the free length and final constrained (by longitudinal compression) length of the element 28. Holes 2| are provided near the free ends 48 and 48 of the exterior legs of element 28 to re-Q ceive the supporting posts or studs 38 and 48.

The bimetallic element 20 when in an unconstrained position will not function with a snap action. However, upon being longitudinally constrained so as to have an uneven configuration, the element will snap from a lower position (Fig. 2) to an uppenposition (Fig. 5),

A plurality of upstanding posts 38 and 40 are rigidly attached to the supporting structure l2 near diametrically opposite corners thereof. The posts 38 and '40 are adapted to be insertedin holes 2! in the free ends of the N-shaped bimetallic element '20. However, it is desired to emphasize the following construction: lines passing through holes 2| parallel to the ends of elethe legend-Free len th in Fig. 1. before the element 28 is assemble and are a lesser distance apart corresponding to the legend Final length when the element is assembledon posts 38 and 40.

Accordingly, since the element 20 is rigidly attached to the posts 38 and 40, such element is constrained into an uneven or buckled configuration with the larger or free movable end portions 42 and 44 thereof being either below or above the level of the free ends 46 and 48 thereof which are rigidly attached to the posts '38 and 40, respectively. It follows that as the temperature of the bimetallic element 20 is changed, the element 20 will flex from the normal lower position (Fig. 2) to an upper position, as shown in Fig. 5. In other words the larger or free movable end portions 42 and 44 will snap upwardly with respect to the fixed ends 36 and 48 of the element 20. In otherwords, the'central portion of the bimetallic element 28 will move with a powerful linear snap-acting motion along a plane substantially normal to the central portion of the element 20. The thermostat i8 embodying my invention utilizes this linear motion of the central portion of the element to operate .the '00- operating contacts H and IS.

The adjusting screw 32 is threadedly engaged or attached to the supporting structure I 2 and to a suitable bushing or sleeve i5 attached there-, to. along the longitudinal axis of the supporting structure {2 and element 2!! and the upper end thereof is located intermediate the element -2ll and structure l2. It is, therefore, obvious that as the adjusting screw 32 is rotatedthe upper end thereof will be moved either upwardly or downwardly depending upon the rotation of such screw. An annular slot 38 in which one end of contact arm i8 is loosely disposed; is located within the upper portion of the screw and is like-- wise moved as the screw 32 is located within the sleeve til. 6

The calibrating screw 28 is, in this instance,

I likewise located along the longitudinal axis of the supporting structure at a point somewhat near the opposite end from that of the adjusting screw 32. However, this particular location is not essential and any other suitable arrangement for positioning the left hand end of arm l8 may be employed. An adjustable nut 54 is positioned upon the upper end of the calibrating screw 28 to preventthe' ready removal of the contact arm 88 and to permit calibration of the closing temperature of the thermostat as hereinafter described.

A suitable link member 55 is used to connect per position, with say, an increase in temperature thereof. the link 56 moving therewith will move the contact arm l8 likewise upwardly so as to disengage the cooperating contact (see Fig. 5).

Then as the temperature of the bimetallic elernent decreases, the element flexes to its normal or engaged position, the link 56 likewise forcing the contact arm l8 downwardly, reengaging the cooperating contacts. I

As the bimetallic element 20 and contact arm It moves from the lower to an upper position, the contact arm I8 in effect rotates around a point within the annular groove 30 of adjusting screw 32 as an axis. It is, therefore, obvious that as such adjusting screw is either lowered or raised, the corresponding movement is directed to I the contact arm I8 and, therefore, may be used to raise or lower the operating range of the thermostat.

The adjusting screw is located substantially It is, theref6re, obvious that I have provided a" thermostatic structure having a bimetallic heat responsive element comprising an elongated substantially N-shaped member which is longitudinally compressed or constrained by attachment at eachend thereof to a supporting structure whereby such element is adapted .to move from an operative to an inoperative position or vice versa and by means of suitable linking members to correspondingly actuate suitable cooperating contacts.

While I have shown my invention in but one v the appended claims.

ill

I'claim as my invention:

1. In a thermostat having a supporting structure and cooperating contacts, a bimetallic heat-responsive element comprising an elongated substantially N-shaped member having two outer the central portion of the middleleg of the N- shaped bimetallic element to the contact arm i8.

. Such link member 56 may, if desired, be punched from, or be integral with the contact arm is. A

plurality of undercut portions 51 arev located when the bimetallic elementfitl flexes to an upw legs, said outer legs being longitudinally compressed by attachment of the free ends thereof to the supporting structure for producing a snap action of such element in response to changes in temperatures thereof.

2. In a thermostat having a supporting struc ture and cooperating contacts, a bimetallic heatresponsive element comprising an elongated substantially N-shaped member having two outer legs, said outer legs being longitudinally compressed by attachment of the free ends thereof 7 to the supporting structure for producing a snap action of such element in response to changes in temperatures thereof, and means associated with the bimetallic element and cooperating contacts for engaging and disengaging such contacts in response to the movements of the element.

3. A thermostat comprising, in combination, a

supporting structure, cooperating contacts, an

elongated bimetallic element having longitudinal slots therein, one extending from each end thereof, formingan N-shaped member, the ends of the exterior legs of said member being attached to the support to reduce the length of e supporting structure, cooperating contacts, anelongated bimetallic. element having longitudinal slots therein; one extending from each end thereof, forming an N-shaped member, the ends said member being attached to the support to reduce the length of the bimetallic element and to ensure a snap action thereof, a contact arm swingably mounted intermediate the bimetallic element and support for carrying at least one 01 said cooperating contacts; and means engaging arm soas to movelthe arm in response to the movements 01' the bimetallic element.

5. A thermostat comprising, in combination, a supporting structure, a bimetallic element mounted substantially from the supporting structure, a contact arm tulcrumlymounted intermediate the bimetallic element and supporting structure, cooperating contacts, including at least one movable contact insulatedly attached to the vcontact arm, adjusting means cooperating with the arm for adjustably limiting the movements thereof, said bimetallic element consisting of a central-strip and two exterior stripsthe ends of which are positioned di-s ametrically opposite for coirfpressibly mounting of the exterior legs of the element to the supporting structure whereupon said central strip is under tension. and means Joining the central strip and contact arm for moving such arm in response to the movements of the element.

6.- A thermostat comprising, supporting structure, an elongated substantially N-shaped bimetallic member longitudinally conthe element and contact parallel to and spaced.

strained by said supporting structure whereby thieexterior legs of said member are under compression' and the cross leg is under tension for producing a snap acting movement of the cross leg, said movementbeing substantially lineal and normal to the plane of said member.

'7. In a thermostat having a supporting strucin combination, a

ture, a bimetallic heat-responsive element com-' prising an elongated substantially N-shaped member having two outer legs, said element having a longitudinal compressive iorce applied ext'eriorly thereto through attachment of the free ends. of said outer legs to the supporting structure.

CHARLES S. MERTLER. 

